Testing High-Quality Optics

Anne L. Fischer

Optics are everywhere. They’re in increasingly sophisticated research and medical devices such as astronomical telescopes and micrographic lenses. They’re also in specialized telecommunications equipment. Sizes, shapes and requirements all vary, bringing new challenges to the manufacturing and testing processes.

Before very high quality optics can be tested, they must, of course, be manufactured, and this is where the issue of the quality of the glass is of concern. Traditional phase-shifting interferometry methods can be difficult and time-consuming, and yet the new optics used in advanced applications demand higher levels of homogeneity of the glass.

The surface geometry of an optical component is also a consideration. When designs call for shapes other than the traditional spheres, process-control metrology is challenged. White-light interferometry can offer a solution for measuring nonspherical surfaces. Techniques such as this may play a leading role in measuring unusual optics, which will become increasingly common with improvements in manufacturing methods such as diamond turning, fine-scale etching and computer-controlled machining.

The following articles tackle two important areas of optics testing. We look at a new testing technology and two new surface measurement techniques that raise the accuracy of testing optics to new heights.